VTT is proud to finally announce our "Spline Lock" crank hub solution for the N54/N55/S55 BMW platforms. After 8 months of testing, and 10+ design changes we arrived at our final design, and exhaustively tested it on the bench, and in our shop test vehicle!
The way this product works is very much like a splined extractor used to remove broken off nipples of fasteners. As you turn the extractor one direction it will lock itself to the nipple, and spin it out. Our hubs are machined to a very close tolerance and are a specific press fit for the crank. You use the crank bolt to install the hub just as you would a stock hub, but for these, you have to lock the crank first, and as you tighten the bolt you will press the splines into the crank creating teeth, and it will be locked. The teeth are designed in such a way that if you have an event that would normally slip a stock hub the teeth will be forced deeper into the crank not allowing it to spin. The benefits of these are two-fold.
1. A positive locking hub.
2. No additional labor to completely disassemble your motor, drill, and pin your crank.
Check the vid:
Some may wonder why did not make a complete CNC hub including the oil sprocket, that is a good question, and one we tried while testing. We found the oil sprocket is almost never to blame when you slip a hub. You are trying to maintain the crank to cam timing, and this is lost either two ways in almost every test we saw. 1. The single grip disc between the timing sprocket and the hub would slip first (most common failure point). Going with a one-piece hub/timing sprocket locked to the crank eliminates that failure point. 2. The bolt itself would spin loose causing this first grip disc to slip, and timing to be lost. Coupling the "Spline Lock" hub with our Crank Bolt Capture eliminates this failure point as well, which is why we suggest running the CBC with the Splined hub.
A great question was asked on facebook regarding the crank, and its hardness in that area to hold the spline created by the hub. When we cut the cranks up for our test rig, Tony took one to the local company that does our annealing, hardening, heat treating, metal analysis, etc. BMW has the crank in that area very hard for durability and longevity. This information was incorporated into the development phase. 17-4 is a SS that can be hardened through annealing and heat treating. We made sure even though the crank was very hard in that area, our hub was even harder to ensure proper spline creation when the hub is pressed into the crank. For comparison, a stock hub would not even read on the Rockwell scale when tested.... that's how soft they are!
See pics below (yes we know oil gear is on backward -it was easier to get the splines in the photo that way!)
Hardness specs as tested: (HRC)
Crank journal (nitrated, tested for fun): 43-47 Rockwell VERY
VERY hard as you would imagine it should be for a journal
Crank hub area: 23 Rockwell (this is very hard)
Our crank hub: 37 Rockwell (extremely hard, and when you anneal 17-4 it becomes a very durable SS even at that hardness)
Stock Hub: The hardwell machine would simply put dimples in it, and not read. (Extremely soft)
Intro Pricing Details (units are in stock!): https://www.e90post.com/forums/showt...5#post23866265